Research on children's world learning has made significant progress in determining how learners acquire word-referent pairings in one and/or across multiple learning events. However, this body of work has a striking limitation: research has focused on acquisition, rather than retention and retrieval of word-referent pairings across time. Consequently, little is known about if and how learners retain and retrieve pairings over varying timescales. The current proposal aims to characterize a developmental trajectory of cross-situational word learning (XSWL) to elucidate the cognitive processes that support and/or constrain development across early childhood (16 to 36-month-old children). The long-term goal of this proposal is to describe how children retain and retrieve words across real-world periods of time-such as days, weeks, and years. Specific Aim I: To characterize children's developing ability to retain and retrieve pairings during XSWL. Specific Aim II: To elucidate the roles of memory and language development in children's XSWL. Methodology: Across three experiments, children will be presented with a typical cross-situational word learning (XSWL) paradigm. Children will be presented with a series of ambiguous learning events close together in time, each consisting of multiple novel words (wug, dax) and multiple novel objects. Across learning events, one word will always co-occurs with one object. After the learning phase, children will receive a word learning test. The testing procedure will use a forced-choice task: the experimenter will ask the child to point to the target/named object (the experimenter will say: Can you point to the 'dax'?). Children will be presented with learning and testing events at several time points to capture retention and retrieval abilities across varying timescales. Children will also participate in a series of working memory, long-term memory, and language development tasks to capture those cognitive processes that may be constraining and/or supporting the developing ability to retain and retrieve words. Significance of Research: The knowledge gained from this work will be invaluable for theories of word learning and designing interventions for populations that are struggling to learn words. Indeed, several clinical populations can readily map words to objects. However, these populations often fail to retain and retrieve words after the learning period. This work will elucidate when and how the ability to retain and retrieve pairings develops in XSWL to one day aid clinicians' identification of atypical developmental trajectories and cognitive processes that may cause learners to struggle to retain and retrieve words.